In the speaker device, in principle, a diaphragm is vibrated by a magnetic field given from a magnetic circuit unit including a magnet and by an electric current flowing through a voice coil, thereby producing the sound. Herein, the magnetic circuit unit serves to vibrate, so to speak, the diaphragm and is installed, it is desired, fixedly with respect to the vibrations of the diaphragm. In fact, however, when driving the speaker, repulsion from the diaphragm forces the magnetic circuit unit itself to be set in some sort of vibrating state, and a sound quality of the speaker device declines as the case may be.
Such being the case, a technology (refer to, e.g., Patent document 1) is proposed, which suppresses the vibrations of the magnetic circuit unit by additionally fitting an anchor to the magnetic circuit unit in order to suppress the vibrations of the magnetic circuit unit that are caused by the repulsion. This technology has a scheme of restraining the decline of the sound quality of the speaker device by additionally fitting the iron-made anchor taking a bowl-like shape to the magnetic circuit unit of the speaker device.
Further, with a rapid spread of the electronic devices of nowadays, the electronic devices disposed adjacent to the speaker device continue to rise in their numbers. Therefore, a technology (refer to, e.g., Patent document 2) is proposed, which restrains the peripheral electronic devices from being affected by the magnetism leaking from the speaker device in a way that controls this magnetism. This technology has a scheme of controlling the magnetism leaking from the speaker device by interposing a magnetic resistance material between a magnetic shielding magnet and a shield cover.    [Patent document 1] Japanese Patent Laid-Open Publication No. 2002-152884    [Patent document 2] Japanese Patent Laid-Open Publication No. S62-38100